I like the idea of an alcohol mod for cars, and i guess using any type of alcohol would work. Rotgut would give the largest capacity out of the alcohols (based on what you said, 11 bottles gives 9 energy? Yeah that should be a bit larger), and others would give less.
Alcohol should give you a speed boost for as long as it is in the system, something like 150-200% of normal speed (would also make cars more desirable). The trade-off could be that the combustion reaction deteriorates your vehicle faster.